1. Field of the Invention
The present invention relates to method for manufacturing a steering wheel.
2. Description of the Related Art
As shown in FIG. 11 and FIG. 12, a steering wheel 51 generally has a steering wheel metal core 52 covered with a covering material 53.
However, in case the covering material 53 put on a ring part metal core 52a of the steering wheel metal core 52 is formed of a soft material such as soft polyvinyl chloride resin or the like, the covering material 53 is capable of turning around the ring part metal core 52a in the direction indicated by an arrow 101. Thus, the feeling of grasping the steering wheel will be lost.
In view of the aforementioned situation, steps are taken such that an adhesive is applied on an outer periphery of the ring part metal core 52a to join the ring part metal core 52a and the covering material 53 together, thereby preventing the covering material 53 from turning.
However, in the steering wheel metal core 52 as manufactured of a rod or the like, since oils or other contaminants stick on the surface of the rod, the adhesive is difficult to stick on the surface of the ring part metal core 52a, which is problematical nevertheless.
Then, to prevent the covering material 53 from turning as described, there is known hitherto an art (Japanese Patent Laid-Open No. 94484/1985), wherein a hardening adhesive is applied on the ring part metal core 52a, the covering material 53 is then formed around the ring part metal core 52a, and thus the adhesive is hardened.
The art is effective in its own way, however, since the adhesive is covered with the covering material 53 on the surface, so long time is required for heating of the adhesive, and thus the manufacturing cycle for manufacturing the steering wheel is prolonged, while a heat gain necessary for reaction of the hardening adhesive cannot be given as the case may be, thus resulting in an unsatisfactory performance with the adhesive. Accordingly, the steering wheel obtained through the aforementioned art still leaves a problem that the covering material 53 is separated to be short in resistance to rotations. The problem is revealed particularly under a high temperature atmosphere standing at 60.degree. to 80.degree. C.